java改错题 求大神解答

1. 你没有创建Class B

   怎么会有构造方法public B()以及怎么new B？？？

2.定义类没有public？？？

public class Circle{

 private double r;

 public Circle(double r){

 this.r = r;

 }

 public double getZhou(){

 return 2*Math.PI*r;

 }

 public double getArea(){

 return Math.PI*r*r;

 }

 public void setR(double r){

 this.r = r;

 }

 public int getR(){

 return r;

 }

}

public class Cylinder extends Circle{

 private double h;

 public Cylinder(double r, double h){

 super(r);

 this.h = h;

 }

 public double getFaceArea(){

 getZhou() * h;

 }

 public double getVolumn(){

 getArea() * h;

 }

 public void setH(double h){

 this.h = h;

 }

 public int getH(){

 return h;

 }

}

classA

{

intx;

publicA(intx)

{    this.x=x；    }

}

public B()//创建类却没有class关键字{}

}